On-channel repeater and on-channel repeating method

ABSTRACT

Provided are an on-channel repeater and method for increasing output of the on-channel repeater by removing feed-back signals caused by low isolation of transmission/reception antennas. The on-channel repeater includes: a receiver for receiving RF signals and converting the RF signals into baseband signals; a subtractor for subtracting replicas of feedback signals from the received signal; an inverse channel estimator for estimating inverse of a reception channel and generating a filter tab coefficients; a first adaptive filter for compensating for channel distortion of the subtracted signal; a transmitter for converting the signals whose channel distortion is compensated into an RF signal and performing radio transmission; a down-converter for down-converting the RF signal converted by the transmitter into the baseband signal; and a replica generator for calculating replicas and feeding back the replicas to the subtractor. The present invention is applied to the on-channel repeater.

TECHNICAL FIELD

The present invention relates to an on-channel repeater and anon-channel repeating method; and, more particularly, to a repeater forrepeating an output signal the same as an input signal on channel byremoving feedback signals caused by low isolation of atransmission/reception antenna by converting a transmitted RadioFrequency (RF) signal into a signal of a predetermined band andsubtracting a replica of the feedback signal from the converted signal,and by compensating for channel distortion of a reception signal byestimating an inverse of reception channel from a signal acquired byremoving the feedback signal, and an on-channel repeating method.

This work was supported by the IT R&D program for MIC/IITA[2007-S-006-01, “Development of On-Channel RF repeating technology basedon OFDM modulation”].

BACKGROUND ART

Repeaters are set up in an area where signals are weakly received from amain transmitter to resolve a problem of instable signal reception andwiden signal transmission coverage of the main transmitter.

FIG. 1 shows a conventional repeating system where different frequenciesare used among the repeaters.

Referring to FIG. 1, a main transmitter 101 transmits a signal of afrequency A and each of repeaters 102 to 105 repeats a signal offrequencies B, C, D and E, respectively, which are different from thefrequency A. The conventional repeating system uses signals of thefrequencies B, C, D and E, which are different for the repeater 102 to105 respectively. Since a plurality of frequency bands are used, manyfrequency resources are required and it is inefficient in the respect ofusing the frequency.

FIG. 2 shows another conventional repeating system where the samefrequency is used among repeaters.

A main transmitter 201 transmits a signal of a frequency A andon-channel repeaters 202 to 205 repeat the signal in the same frequencyA. The signals of the same frequency transmitted from the maintransmitter 201 and the on-channel repeaters 202 to 205 should beindividually identified for on-channel repeating.

However, when the signals of the same frequency band outputted from themain transmitter and the repeaters are different, the signals are notremoved as on-channel interference signals by an equalizer or otherdevices in each repeater.

Also, when the signals transmitted from the main transmitter and theon-channel repeaters have a time delay longer than a predeterminedlevel, the equalizer cannot remove the delayed signal. Therefore, theoutput signals of the on-channel repeater should be the same as theoutput signals of the main transmitter for on-channel repeating, and thetime delay of two output signals should be short.

Problems of the conventional on-channel repeaters will be described withreference to FIGS. 3 to 7.

FIG. 3 is a block diagram showing a conventional RF amplificationon-channel repeater.

Referring to FIG. 3, a reception antenna 301 and an RF receiver 302receive RF signals transmitted from the main transmitter. An RFband-pass filter 303 passes only signals of a predetermined signal bandin the received RF signals and a high-power amplifier 304 amplifies theband-passed RF signals. The amplified RF signal is transmitted throughon-channel through a transmission antenna 305.

FIG. 4 is a block diagram showing a conventional Intermediate Frequency(IF) conversion on-channel repeater.

Referring to FIG. 4, a reception antenna 401 and an RF receiver 402receive RF signals transmitted from the main transmitter. An IFdown-converter 403 converts the received RF signals into IF signalsbased on a reference frequency provided by a local oscillator (LO) 408.An IF band-pass filter 404 passes the IF signals of a predeterminedband. An RF up-converter 405 converts the band-passed IF signals into nRF signals based on the reference frequency provided by the localoscillator 408. A high-power amplifier 406 amplifies the RF signals andthe amplified RF signals are transmitted through a transmission antenna407.

FIG. 5 is a block diagram showing a conventional on-channel repeateremploying surface acoustic wave (SAW) filter.

Referring to FIG. 5, a reception antenna 501 and an RF receiver 502receive RF signals transmitted from the main transmitter and an IFdown-converter 503 converts the received RF signals into IF signal basedon a reference frequency provided by a local oscillator 508.

A SAW filter 504 passes IF signals of a predetermined band. An RFup-converter 505 converts the band-passed IF signals into RF signalsbased on the reference frequency provided by the local oscillator 508. Ahigh-power amplifier 506 amplifies the RF signals and the amplified. RFsignals are transmitted through a transmission antenna 507.

Since the on-channel repeater of FIGS. 3 to 5 cannot remove noise andmulti-path signals caused in a channel between the main transmitter andthe on-channel repeater, feedback signals caused by low isolation of atransmission/reception antenna, and system noise added in an on-channelrepeater system, it has a characteristic that an output signal isinferior than an input signal. Also, there is another problem in thatthe feedback signals generated due to the low isolation of thetransmission and reception antennas restrict the transmission outputpower of the on-channel repeaters.

FIG. 6 is a block diagram showing a conventional on-channel repeaterperforming a modulating/demodulating procedure.

Referring to FIG. 6, a reception antenna 601 and an RF receiver 602receive RF signals transmitted from the main transmitter. An IFdown-converter 603 converts the received RF signals into IF signalsbased on a reference frequency provided by a local oscillator 611. Ademodulator 604 demodulates the IF signals into baseband signals. Anequalizing and forward error correction (FEC) decoding unit 605 removenoise and multi-path signals caused in a channel between the maintransmitter and the on-channel repeater from the demodulated basebandsignal, and feedback signals caused by low isolation of atransmission/reception antenna. A FEC decoder 606 performs coding forerror correction of output signals of the equalizing and FEC decodingunit 605. A modulator 607 converts the FEC encoded signals into signalsof an IF band. An RF up-converter 608 converts the IF signals into an RFsignal based on a reference frequency provided by a local oscillator611. A high-power amplifier 609 amplifies the RF signals and theamplified RF signals are transmitted through a transmission antenna 610.

Through the equalizing and FEC decoding unit, the on-channel repeater ofFIG. 6 improves the multi-path and noise removing capability which isthe problem of the repeater shown in FIGS. 3 to 5. However, since theon-channel repeater includes the equalizing and FEC decoding unit, itincreases time delay from a microsecond unit to a millisecond unit. Inaddition, the transmission output power is limited when the feedbacksignals generated by ambiguity of a standard Trellis encoder of the FECencoder is not removed in the repeater.

FIG. 7 is a block diagram showing a conventional on-channel repeatercapable of compensating for distortion of a reception channel.

Referring to FIG. 7, an RF receiver 701 receives RF signals transmittedfrom the main transmitter and a down-converter 702 converts the receivedRF signals into signals of a desired band.

An inverse channel estimator 703 estimates an inverse of the receptionchannel including noise and multi-path signals caused in a channelbetween the main transmitter and the repeater from the converted signal,and feedback signals caused by low isolation of a transmission/receptionantenna.

An adaptive filter 704 compensates for channel distortion based oninverse information of the estimated reception channel.

An up-converter 705 converts the compensated signals into RF signal andan RF transmitter 706 transmits the converted RF signals.

When the electric field strength of feedback signals (which are causedby low isolation of the transmission and reception antennas) is higherthan the electric field strength of the input signal transmitted frommain transmitter, the on-channel repeater of FIG. 7 does not removedistortion signals in the adaptive filter and does not estimate aninverse of the reception channel in the inverse channel estimator,thereby causing malfunction of the repeater.

Since the conventional technologies have a limitation in their removingcapability of feedback signals, the conventional on-channel repeatingsystems have a low applicability in using a typical repeating facilityand require a great deal of investment.

Therefore, it is required to develop an on-channel repeater havingcharacteristics that the output signals of the on-channel repeater isthe same as the output signals of the main transmitter, that the timedelay between two output signals is small, that a characteristic of theon-channel repeater output signal becomes superior to that of theon-channel repeater input signal by removing the noise and multi-pathsignals caused in the channel between the main transmitter and theon-channel repeater, and that the applicability is raised and the smallamount of investment is required by increasing transmission output powerof the on-channel repeater by removing the feedback signals caused bythe low isolation of transmission and reception antennas in theon-channel repeater.

DISCLOSURE Technical Problem

An embodiment of the present invention is directed to providing arepeater for repeating an output signal the same as an input signal onchannel by removing feedback signals caused by low isolation of atransmission/reception antenna from a transmitted Radio Frequency (RF)signal and compensating for channel distortion of a reception signal byestimating an inverse of a reception channel from a signal acquired byremoving the feedback signal, and an on-channel repeating method.

Technical Solution

In accordance with an aspect of the present invention, there is providedan on-channel repeater, including: a receiver for receiving a RadioFrequency (RF) signal and converting the RF signal into a basebandsignal; a subtractor for subtracting a replica of feedback signals fromthe signal received in the receiver; an inverse channel estimator forestimating an inverse of a reception channel based on the signalacquired from the subtraction in the subtractor and generating filtertab coefficients; a first adaptive filter for compensating for channeldistortion of the signal acquired from the subtraction in the subtractorbased on the filter tab coefficients generated by the inverse channelestimator; a transmitter for converting the signal whose channeldistortion is compensated by the first adaptive filter into an RF signaland performing radio transmission; a down-converter for down-convertingthe RF signal acquired in the transmitting means into a baseband signal;and a replica generator for calculating a replica based on the basebandsignal acquired from the conversion in the down-converting means and thesignal acquired from the subtraction in the subtractor, and feeding backthe replica to the subtractor.

In accordance with another aspect of the present invention, there isprovided an on-channel repeating method, including: receiving an RFsignal and converting the RF signal into a baseband signal; subtractinga replica of feedback signals from the received signal; estimating aninverse of a reception channel based on the signal acquired from thesubtraction, and generating filter tab coefficients; compensating forchannel distortion of the signal acquired from the subtraction based onthe generated filter tab coefficients; performing radio transmission byconverting the signal whose channel distortion is compensated into an RFsignal; and down-converting the RF signal acquired in the transmittingmeans into a baseband signal, where the replica is calculated based onthe baseband signal acquired from the down-conversion and the signalacquired from the subtraction, and is fed back to said subtracting thereplica of the feedback signal.

In accordance with another aspect of the present invention, there isprovided an on-channel repeater, including: a receiver for receiving anRF signal and converting the RF signal into a predetermined band signal;a subtractor for subtracting a replica of feedback signals from thesignal received in the receiver; an inverse channel estimator forestimating an inverse of a reception channel based on the signalacquired from the subtraction in the subtractor and generating filtertab coefficients; a first adaptive filter for compensating for channeldistortion of the signal acquired from the subtraction based on thefilter tab coefficients generated by the inverse channel estimator; atransmitter for converting the signal whose channel distortion iscompensated by the first adaptive filter into an RF signal andperforming radio transmission; a down-converter for down-converting theRF signal acquired in the transmitting means into a predetermined bandsignal; and a replica generator for calculating a replica based on thepredetermined band signal acquired from the conversion in thedown-converter and the signal acquired from the subtraction in thesubtractor, and feeding back the replica to the subtractor.

In accordance with another aspect of the present invention, there isprovided an on-channel repeating method, including: receiving an RFsignal and converting the RF signal into a predetermined band signal;subtracting a replica of feedback signals from the received RF signal;estimating an inverse of a reception channel based on the signalacquired from the subtraction in said subtracting the replica of thefeedback signals, and generating filter tab coefficients; compensatingfor channel distortion of the signal acquired from the subtraction basedon the generated filter tab coefficients; performing radio transmissionby converting the signal whose channel distortion is compensated into anRF signal; and down-converting the RF signal acquired in thetransmitting means into the predetermined band signal, wherein thereplica is calculated based on the predetermined band signal convertedin the step of down-converting the RF signal and the signal acquiredfrom the subtraction in the step of subtracting the replica of thefeedback signal, and is fed back to said subtracting the replica of thefeedback signal.

ADVANTAGEOUS EFFECTS

As described above, the present invention can increase efficiency oflimited frequency resources by repeating a signal that is the same asoutput signal of a main transmitter, has a short time delay between theoutput signals of the on-channel repeater and the main transmitter, andhas its distortion caused in a transmission channel compensated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional repeating system using differentfrequencies.

FIG. 2 shows a conventional repeating system using the same frequency.

FIG. 3 is a block diagram showing a conventional Radio Frequency (RF)amplification on-channel repeater.

FIG. 4 is a block diagram showing a conventional Intermediate Frequency(IF) conversion on-channel repeater.

FIG. 5 is a block diagram showing a conventional on-channel repeateremploying a surface acoustic wave (SAW) filter.

FIG. 6 shows a conventional on-channel repeater performing amodulating/demodulating procedure.

FIG. 7 is a block diagram showing a conventional on-channel repeatercapable of compensating for distortion of a reception channel.

FIG. 8 is a block diagram showing an on-channel repeater in accordancewith an embodiment of the present invention.

FIG. 9 is a flowchart describing a repeating method in the on-channelrepeater of FIG. 8.

FIG. 10 is a block diagram illustrating the on-channel repeater of FIG.8.

FIG. 11 is a flowchart illustrating the repeating method in theon-channel repeater of FIG. 8

FIG. 12 is a block diagram illustrating an inverse channel estimator ofFIG. 8.

FIG. 13 is a block diagram showing a demodulating unit of FIG. 12 and itmay be applied to the DVB-T DTV standard.

FIG. 14 is a block diagram showing a channel estimating unit of FIG. 12and it may be applied to the DVB-T DTV standard.

FIG. 15 is a block diagram showing a converting unit 1203 of FIG. 12 andit may be applied to the DVB-T DTV standard.

FIG. 16 is a block diagram showing the on-channel repeater in accordancewith another embodiment of the present invention.

BEST MODE FOR THE INVENTION

The advantages, features and aspects of the invention will becomeapparent from the following description of the embodiments withreference to the accompanying drawings, which is set forth hereinafter.The preferred embodiments of the present invention will be described indetail hereinafter with reference to the attached drawings.

FIG. 8 is a block diagram showing an on-channel repeater in accordancewith an embodiment of the present invention.

Referring to FIG. 8, the on-channel repeater in accordance with thepresent invention includes a reception antenna 801, a Radio Frequency(RF) receiver 802, a subtractor 803, a replica generator 804, an inversechannel estimator 805, a first adaptive filter 806, an RF transmitter807, a down-converter 808, and an RF transmission antenna 809.

The RF receiver 802 down-converts RF signals transmitted from a maintransmitter or another repeater through the reception antenna 801 intosignals of a desired band.

The subtractor 803 removes feedback signals by subtracting a replica offeedback signals from the predetermined band signal down-converted bythe RF receiver 802.

The replica generator 804 generates a replica of the feedback signalsbased on signal acquired from the down-conversion into signal of apredetermined band by the down-converter 808 and a signal outputted fromthe subtractor 803, i.e., a signal acquired by removing the feedbacksignals, and feeds back the replica to the subtractor 803.

The inverse channel estimator 805 generates filter tab coefficients byestimating an inverse of a reception channel including noise, multi-pathsignals and remaining feedback signals based on the signal outputtedfrom the subtractor 803. Herein, the remaining feedback signals meanfeedback signals which is not removed through subtraction in thesubtractor 803.

In accordance with the present invention, the subtractor 803 and thereplica generator 804 only remove the feedback signals but do not affectthe time delay of the repeater system.

The first adaptive filter 806 compensates for the channel distortion ofthe signal outputted from the subtractor 803 by performing filteringaccording to Equation 1 based on the filter tab coefficients generatedby the inverse channel estimator 805.

$\begin{matrix}{{z(n)} = {\sum\limits_{i = 0}^{N - 1}\; {c_{i} \cdot {ɛ\left( {n - 1} \right)}}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

where, ε(n) is an output signal of the subtractor 803, z(n), is anoutput signal of the first adaptive filter 806, c_(I) is a tabcoefficient c=c₀, c₁, . . . , c_(N−1)) estimated by the inverse channelestimator 805, and N is the number of tabs.

The RF transmitter 807 converts the signal outputted from the firstadaptive filter 806 into RF signal and performs radio transmissionthrough the RF transmission antenna 809.

The down-converter 808 down-converts the RF signal converted by the RFtransmitter 807 into signal of a predetermined band.

FIG. 9 is a flowchart describing a repeating method in the on-channelrepeater of FIG. 8.

Referring to FIG. 9, RF signal transmitted from the main transmitter oranother repeater is received through the reception antenna 801 and isdown-converted into signal of a desired band in the RF receiver 802 atstep S901.

The subtractor 803 removes feedback signals from the output signal ofthe RF receiver 802 at step S902 by subtracting a replica of thefeedback signals generated in the replica generator 804 from the signaloutputted from the RF receiver 802.

The replica generator 804 generates replica of the feedback signalsbased on a signal down-converted into signal of a predetermined band bythe down-converter 808 and a signal outputted from the subtractor 803,i.e., signal whose feedback signals are first removed, and feeds backthe replica to the subtractor 803 at step S903.

The inverse channel estimator 805 generates filter tab coefficients byestimating an inverse of the reception channel including noise,multi-path signals and remaining feedback signals based on the signaloutputted from the subtractor 803 at step S904.

The first adaptive filter 806 compensates for the channel distortion ofthe signal outputted from the subtractor 803 based on the filter tabcoefficients generated by the inverse channel estimator 805 at stepS905.

The RF transmitter 807 converts the signal outputted from the firstadaptive filter 806 into RF signal and wirelessly transmits the signalthrough the RF transmission antenna 809 at step S906.

The down-converter 808 down-converts the RF signal converted by RFtransmitter 807 into signal of a predetermined band at step S907.

FIG. 10 is a block diagram illustrating the on-channel repeater of FIG.8.

Therefore, a reception antenna 1001, an RF receiver 1002, an inversechannel estimator 1005, a first adaptive filter 1006, an RF transmitter1007, and a transmission antenna 1009 correspond to the receptionantenna 801, the RF receiver 802, the inverse channel estimator 805, thefirst adaptive filter 806, the RF transmitter 807, and the RFtransmission antenna 809.

Meanwhile, a replica generator 1004 includes a filter coefficientgenerator 1010 and a second adaptive filter 1011. The filter coefficientgenerator 1010 generates filter tab coefficients used in the secondadaptive filter 1011 based on the signal acquired from thedown-conversion into signal of a predetermined band by thedown-converter 1008 and signal outputted from a subtractor 1003. Thesecond adaptive filter 1011 generates replica of feedback signals basedon filter tab coefficients generated in the filter coefficient generator1010 and the signal acquired from the down-conversion into signal of apredetermined band by the down-converter 1008. The second adaptivefilter 1011 feeds back the replica to the subtractor 1003.

The filter coefficient generator 1010 calculates filter tab coefficientsh_(n) in a time index n according to Equation 2 based on a Least MeanSquare (LMS) algorithm.

h _(n) = h _(n−1) +λ·ε(n)· s_(n) *

h _(n) =[h ₀(n)h ₁(n) . . . h_(M−1)(n)]^(T)

h _(n−1) =[h ₀(n−1)h ₁(n−1) . . . h _(M−1)(n−1)]^(T)

s _(n) =[s(n)s(n−1) . . . s(n−M+1)]^(T)  Eq. 2

where s_(n) is a signal vector acquired from the down-conversion intosignal of a predetermined band by the down-converter 1008 in a timeindex n; ε(n) is an output signal of the subtractor 803 in the timeindex n; h_(n−1) is filter tab coefficients in a time index (n−1); λ isa constant for determining a convergence speed; M is a transpose; and *is a complex conjugate.

The second adaptive filter 1011 calculates a replica fb(n) of thefeedback signal according to Equation 3 by filtering the down-convertedsignal vector s_(n) outputted from the down-converter 1008 based onfilter tab coefficients h_(n) generated in the filter coefficientgenerator 1010.

fb(n)= h _(n) ^(T)· s _(n)   Eq. 3

According to Equation 4, the subtractor 1003 removes the feedbacksignals caused by low isolation of the transmission/reception antenna bysubtracting replica fb(n) of feedback signals calculated in the secondadaptive filter 1011 in an output signal r(n) of the RF receiver 1002.

ε(n+1)=r(n)−fb(n)  Eq. 4

FIG. 11 is a flowchart illustrating the repeating method in theon-channel repeater of FIG. 8.

Referring to FIG. 11, RF signal transmitted from the main transmitter oranother repeater is received through the reception antenna 1001, anddown-converted into signal of a desired band in the RF receiver 1002 atstep S1101.

The subtractor 1003 removes feedback signals from the output signal ofthe RF receiver 1002 by subtracting a replica of feedback signalsgenerated in the second adaptive filter 1006 from the signal outputtedfrom the RF receiver 1002 at step S1102.

The filter coefficient generator 1010 of the replica generator 1004generates filter tab coefficients in the second adaptive filter 1011based on signal acquired from the down-conversion into signal of apredetermined band by the down-converter 1008 and signal outputted fromthe subtractor 1003 acquired by removing the feedback signals at stepS1103. The second adaptive filter 1011 generates a replica of feedbacksignals by filtering the output signal of the down-converter 1008 basedon the filter tab coefficients generated in filter coefficient generator1010, and feeds back the a replica to the subtractor 1003 at step S1104.

The inverse channel estimator 1005 generates filter tab coefficients byestimating an inverse of the reception channel including noise,multi-path signals and remaining feedback signals caused in thereception channel based on the signal outputted from the subtractor 1003at step S1105.

The first adaptive filter 1006 compensates for channel distortion of thesignal outputted from the subtractor 1003 based on the filter tabcoefficients generated by the inverse channel estimator 1005 at stepS1106.

The RF transmitter 1007 converts the signal outputted from the firstadaptive filter 1006 into an RF signal and performs radio transmissionthrough the transmission antenna 1009 at step S1107.

The down-converter 808 down-converts the RF signal converted by the RFtransmitter 807 into signal of a predetermined band at step S1108.

FIG. 12 is a block diagram illustrating the inverse channel estimator805 of FIG. 8.

Referring to FIG. 12, the inverse channel estimator 805 includes ademodulating unit 1201, a channel estimating unit 1202 and a convertingunit 1203.

The demodulating unit 1201 demodulates the signal outputted from thesubtractor 803 through a frequency and timing synchronizing procedure.

The channel estimating unit 1202 estimates channel distortion of therepeater reception channel including noise, multi-path signals andremaining feedback signals caused in a channel between the maintransmitter and the on-channel repeater based on the signal demodulatedby the demodulating unit 1201.

The converting unit 1203 generates filter tab coefficients used in thefirst adaptive filter 806 by estimating an inverse of the receptionchannel from the channel distortion information of the reception channelestimated by the channel estimating unit 1202.

The demodulating unit 1201, the channel estimating unit 1202, and theconverting unit 1203 of FIG. 12 may be formed diversely according tosystem standards.

In FIGS. 13 to 15, embodiments of the demodulating unit 1201, thechannel estimating unit 1202, and the converting unit 1203 in a DVB-TDTV standard using an Orthogonal Frequency Division Multiplexing (OFDM)modulating technique will be described hereinafter.

FIG. 13 is a block diagram showing the demodulating unit 1201 of FIG. 12and it may be applied to the DVB-T DTV standard.

The demodulating unit 1201 includes a guard interval remover 1301, aserial-to-parallel converter (SPC) 1302, and a Fast Fourier Transformer(FFT) 1303.

The guard interval remover 1301 removes a guard interval from a signaloutputted from the subtractor 1003. The serial-to-parallel converter1302 converts the signal whose guard interval is removed by the guardinterval remover 1301 into a parallel signal. The Fast FourierTransformer 1303 converts the parallel signal converted by theserial-to-parallel converter 1302 into a frequency domain.

FIG. 14 shows the channel estimating unit 1202 of FIG. 12 and it may beapplied to the DVB-T DTV standard.

The channel estimating unit 1202 includes a pilot extractor 1401, apilot storage 1402 and a channel distortion estimator 1403.

The pilot extractor 1401 extracts a pilot signal from an output signalof the demodulating unit 1201. The pilot storage 1402 stores apredetermined pilot signal. The channel distortion estimator 1403estimates channel distortion by comparing the pilot signal extracted bythe pilot extractor 1401 with the pilot signal stored in the pilotstorage 1402.

FIG. 15 is a block diagram showing the converting unit 1203 of FIG. 12and it may be applied to the DVB-T DTV standard.

The converting unit 1203 includes an inverse converter 1501 and atime-domain converter 1502.

The inverse converter 1501 generates inverse of channel distortion basedon channel distortion information estimated by channel estimating unit1202.

The time-domain converter 1502 converts the inverse of the channeldistortion generated in the inverse converter 1501 into filter tabcoefficients of time domain.

FIG. 16 is a block diagram showing the on-channel repeater in accordancewith another embodiment of the present invention.

FIG. 16 has the same format as FIG. 8 except that a signal is convertedinto a baseband signal in a transmitter/receiver.

Therefore, a subtractor 1606, a replica generator 1607, an inversechannel estimator 1608 and a first adaptive filter 1609 individuallycorrespond to the subtractor 803, the replica generator 804, inversechannel estimator 805 and the first adaptive filter 806, respectively.

An RF receiver 1602 receives RF signal from the main transmitter oranother repeater through the reception antenna 1601.

A first Intermediate Frequency (IF) down-converter 1603 down-convertsthe received RF signal into IF signal based on a reference frequencyprovided from a local oscillator 1617. A first analog-to-digitalconverter 1604 converts the analog IF signal outputted from the first IFdown-converter 1603 into digital IF signal. The first baseband converter1605 converts the output signal of the first analog-to-digital converter1604 into baseband signal.

An IF up-converter 1610 converts the signal outputted from the firstadaptive filter 1609 into IF signal. A digital-analog converter 1611converts the digital IF signal outputted from the IF up-converter 1610into analog IF signal. An RF up-converter 1612 up-converts the outputsignal of the digital-analog converter 1611 into RF signal based on areference frequency provided from the local oscillator 1617.

The RF signal acquired from the up-conversion in the RF up-converter1612 is amplified by the high-power amplifier 1613.

Through the second IF down-converter 1614, the RF signal amplified bythe high-power amplifier 1613 is down-converted into signal of IF bandwhich is the same as the band of analog IF signal acquired from thedown-conversion in the first IF down-converter 1603 based on thereference frequency provided from the local oscillator 1617.

A second analog-to-digital converter 1615 converts the output signal ofthe second IF down-converter 1614 into digital IF signal. A secondbaseband converter 1616 converts the output signal of the secondanalog-to-digital converter 1615 into baseband signal. The replicagenerator 1607 generates a replica of the feedback signals based on thesignal acquired from the down-conversion into the baseband signals inthe second baseband converter 1616 and outputted signal from thesubtractor 1606, i.e., signal acquired by removing the feedback signals,and feeds back the signal to the subtractor 1606.

That is, a filter coefficient generator 1618 of the replica generator1607 generates filter tab coefficients of a second adaptive filter 1619based on the signal acquired from the down-conversion into basebandsignal by the second baseband converter 1616 and signal outputted fromthe subtractor 1606, i.e., signal acquired by removing the feedbacksignals. The second adaptive filter 1619 generates a replica of thefeedback signals by filtering the signal acquired from thedown-conversion into the baseband signal by the second basebandconverter 1616 based on the filter tab coefficients generated in thefilter coefficient generator 2618.

The local oscillator 1617 generates and provides a reference frequencyto the first IF down-converter 1603, the second IF down-converter 1614,and the RF up-converter 1612.

Although the on-channel repeating method and the on-channel repeaterwhich improve feedback signal removing capability in accordance with thepresent invention are proper to broadcastings such as AdvancedTelevision Systems Committee (ATSC), Digital Video Broadcasting (DVB),Digital Multimedia Broadcasting (DMB) and Integrated Service DigitalBroadcasting-Terrestrial (ISDB-T), and communications such as wirelessbroadband (Wibro) and Code Division Multiple Access (CDMA), they are notlimited to these examples and can be applied anywhere in an environmentwhich requires a repeater to configure a general single frequencynetwork.

As described above, the technology of the present invention can berealized as a program and stored in a computer-readable recordingmedium, such as CD-ROM, RAM, ROM, floppy disk, hard disk andmagneto-optical disk. Since the process can be easily implemented bythose skilled in the art of the present invention, further descriptionwill not be provided herein.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

INDUSTRIAL APPLICABILITY

The present invention can increase efficiency of limited frequencyresources by repeating a signal that is the same as output signal of amain transmitter, has a short time delay between the output signals ofthe repeater and the main transmitter, and has its distortion caused ina transmission channel compensated.

1.-13. (canceled)
 14. An on-channel repeating method, comprising:receiving a Radio Frequency (RF) signal and converting the RF signalinto a predetermined band signal; subtracting a replica of feedbacksignals from the received signal; estimating an inverse of a receptionchannel based on the signal acquired from the subtraction and generatinga filter tab coefficients; compensating for channel distortion of thesignal acquired from the subtraction based on the generated filter tabcoefficients; performing radio transmission by converting the signalwhose channel distortion is compensated into an RF signal; anddown-converting the RF signal acquired in the transmitting means intothe predetermined band signal, wherein the replica is calculated basedon the predetermined band signal acquired from the down-conversion andthe signal acquired from the subtraction and is fed back to saidsubtracting the replica of the feedback signal.
 15. The on-channelrepeating method of claim 14, wherein the replica includes: calculatinga filter tab coefficients in a time index n based on the predeterminedband signal in a time index n, the signal acquired from the subtractionin the time index n, and the filter tab coefficients in a time indexn−1; and calculating a replica based on the filter tab coefficients inthe time index n and the predetermined band signal.
 16. The on-channelrepeating method of claim 15, wherein in said calculating the filter tabcoefficients, a filter tab coefficient vector is calculated based on aLeast Mean Square (LMS) algorithm.
 17. The on-channel repeating methodof claim 16, wherein in said calculating the filter tab coefficients,the filter tab coefficient vector h_(n) is calculated according toEquation 1:h _(n) = h _(n−1) +λ·ε(n)· s _(n) *h _(n) =[h ₀(n)h ₁(n) . . . h _(M−1)(n)]^(T)h _(n−1) =[h ₀(n−1)h ₁(n−1) . . . h _(M−1)(n−1)]^(T)s _(n) =[s(n)s(n−1) . . . s(n−M+1)]^(T)  Eq.1 where s_(n) is a signalvector acquired from the down-conversion into the predetermined band inthe time index n; ε(n) is a signal acquired from the subtraction in thetime index n; λ is a constant for determining a convergence speed; M isthe number of filter tabs; T is a transpose; and * is a complexconjugate.
 18. The on-channel repeating method of claim 17, wherein insaid calculating the replica, the replica fb(n) is calculated accordingto Equation 2:fb(n)= h _(n) ^(T)· s _(n)   Eq. 2
 19. The on-channel repeating methodof claim 18, wherein in said subtracting the replica of the feedbacksignal, the replica is subtracted from the predetermined band signalacquired from the said receiving RF signal and converting the RF signalaccording to Equation 3:ε(n+1)=r(n)−fb(n)  Eq. 3 where r(n) is the predetermined band signalacquired from the conversion in said receiving RF signal and convertingthe RF signal in the time index n; and ε(n+1) is a signal acquired fromthe subtraction in said subtracting the replica of the feedback signalin the time index n+1.
 20. The on-channel repeating method of claim 14,wherein said estimating the inverse of the reception channel includes:demodulating the signal acquired from the subtraction in saidsubtracting the replica of the feedback signal; estimating channeldistortion information of a repeater reception channel based on thesignal acquired from the demodulation in said demodulating the signal;and calculating an inverse of the reception channel based on theestimated channel information and generating a filter tab coefficientsbased on the calculated inverse of the reception channel.
 21. Theon-channel repeating method of claim 20, wherein said demodulating thesignal includes: removing a guard interval of the signal acquired fromthe subtraction in said subtracting the replica of the feedback signal;converting the signal without a guard interval into a parallel signal;and transforming the parallel signal into a frequency domain.
 22. Theon-channel repeating method of claim 20, wherein said estimating channeldistortion information of the repeater reception channel includes:extracting a pilot signal from the demodulated signal; storing apredetermined pilot signal; and estimating channel distortion bycomparing the extracted pilot signal with the stored pilot signal. 23.The on-channel repeating method of claim 20, wherein said calculating aninverse of the reception channel and generating the filter tabcoefficients includes: generating an inverse of channel distortion basedon the estimated channel distortion information; and converting theinverse of the channel distortion into a filter tab coefficients of atime domain.
 24. The on-channel repeating method of claim 14, whereinsaid down-converting the RF signal includes: down-converting the RFsignal acquired from the conversion in said performing radiotransmission into an IF signal; converting the IF signal into a digitalIF signal; and converting the digital IF signal into the predeterminedband signal.
 25. The on-channel repeating method of claim 14, whereinsaid receiving RF signal and converting the RF signal includes:receiving an RF signal; down-converting the RF signal into an IF signal:converting the IF signal into a digital IF signal; and converting thedigital IF signal into the predetermined band signal.
 26. The on-channelrepeating method of claim 14, wherein said performing radio transmissionincludes: converting the signal whose channel distortion is compensatedin the step of compensating for channel distortion of the signal into adigital IF signal; converting the digital IF signal converted in thestep of converting the signal whose channel distortion is compensatedinto the digital IF signal into an analog IF signal; up-converting theanalog IF signal into an RF signal; and amplifying the RF signal.
 27. Anon-channel repeater, comprising: a receiving means for receiving a RadioFrequency (RF) signal and converting the RF signal into a predeterminedband signal; a subtracting means for subtracting a replica of feedbacksignals from the signal received in the receiving means; an inversechannel estimating means for estimating an inverse of a receptionchannel based on the signal acquired from the subtraction in thesubtracting means and generating a filter tab coefficients; a firstadaptive filtering means for compensating for channel distortion of thesignal acquired from the subtraction in the subtracting means based onthe filter tab coefficients generated by the inverse channel estimatingmeans; a transmitting means for converting the signal whose channeldistortion is compensated by the first adaptive filtering means into anRF signal and performing radio transmission; a down-converting means fordown-converting the RF signal acquired in the transmitting means intothe predetermined band signal; and a replica generating means forcalculating a replica based on the predetermined band signal acquiredfrom the conversion in the down-converting means and the signal acquiredfrom the subtraction in the subtracting means, and feeding back thereplica to the subtracting means. 28.-47. (canceled)